Hydraulic pumps (see, e.g., DE 21 14 202 C3) of this type are known in the prior art in a plurality of embodiments. Generally, hydraulic pumps are used to convert mechanical energy in the form of torque and rotational speed into hydraulic energy with a definable volumetric flow and fluid pressure. Hydraulic pumps that work according to the displacement principle have individual chambers sealed in the pump housing. In these chambers fluid is transported from the inlet side of the pump, comprising a suction port, to the outlet side in the form of the pressure port. Since no direct connection is between the suction port and the pressure port, pumps according to the displacement principle are suitable especially for high fluid system pressures.
Depending on whether vanes or pistons are used for implementation of the displacement principle, gear pumps and spiral pumps are distinguished from the vane pumps as dictated by design. Vane pumps are distinguished from the radial and axial piston pumps. All these pumps, regardless of whether the displacement volume is kept constant or variable, the displaced volume commonly and certainly always relates only to a fluid flow that is to be delivered and that is hereinafter referred to as the main flow.